In growing any relatively low row crop, as with soybeans, cotton, and the like, there is a continual needed effort to inhibit or destroy taller, unwanted plants which invade the row crop area. Commonly encountered unwanted plants include volunteer corn, sunflowers, Johnson grass, and other weeds which tower above the desired crop.
Destruction of the unwanted plants is a recognized problem, and many systems and devices have been developed to cope with the problem. A wide variety of sprayers have been used to destroy the unwanted plants, but spraying has its limitations because of the high risk of herbicide spray contacting the desired crop, particularly under windy conditions, and because of the high use rate and high evaporation loss of the costly herbicides used in such spraying. In an effort to conserve or reduce the amount of spray required for weed control, devices are now available which recapture some of the spray, and elaborate shield devices have been designed to try to protect the crop from wayward spray. As a result of these conservation and shielding efforts, herbicide spraying devices have become increasingly expensive to manufacture, complicated to operate and maintain, and the challenge of protecting the crop and substantially reducing herbicide loss during spraying still persists. With the continually increasing cost of chemical herbicide, spraying costs have mounted so substantially that any unnecessary waste of the chemical is to be discourged.
Another direction taken by the industry to provide adequate herbicide application includes direct application of the herbicide to unwanted plants by physical contact between the plants and a moving, saturated mat, canvas, rope or tube. For example, it is known to utilize a horizontally oriented porous tube extending at a level above the protected crop and to move it across the field and into contact against unwanted plants so as to impregnate the plants with herbicide. Related applicators have utilized sponges attached to the porous tubes and various types of matting which is impregnated with the herbicide and dragged over the unwanted plants. All of these devices have the disadvantage of requiring significant quantities of herbicide to saturate the mats and sponges and the significant surface areas of these devices result in high evaporation and drippage losses of the expensive herbicide. More recent devices have utilized horizontal rope or wick-type segments which are impregnated with the herbicide and which are moved across the field and into contact with the unwanted plants. These devices have an advantage over other units in that they do not involve spraying and have lower herbicide losses due to evaporation. While such devices are definite improvements, they still share a common shortcoming in that the rope or wicking, like the canvas and mats, at times becomes so soaked with herbicide that the herbicide drips downwardly onto the soybean or cotton crop, causing destruction and damage to the crop. It is highly important that the applicator apply the herbicide only to the unwanted plants and that it be prevented from reaching the nurtured crop. The present invention provides an improved, simplified, highly efficient and low-loss applicator which is constructed to assure that herbicide does not reach the protected crop.